Clay & Geothermal Heating
After Saturdays’ visit to the Apromer open day, the whole heating question is up for debate. We have been keen for some time on the idea of a geothermal heat pump, but it’s almost impossible to get anyone who’s in the business to say a bad word about the thing they’re selling (naturally).
So to find an objective viewpoint (sort of), we had to go to someone who’s promoting solar energy. Here’s his take, and an anecdote he told to a visitor without us having even mentioned our situation…
You have to admire someone who analyses the pros and cons of an energy source in global terms, rather that merely appealing to he wallet of the individual. M. Philippe Bertrand, our host on the day, did these sums with the commonly stated energy efficiency data about geothermal heating—that is, for 1kW of energy put into the system, you get 3kW back. It goes like this:
- In France, the majority of electricity is produced by heat-producing methods: nuclear, coal, gas…
- To produce 1kW of electricity takes 3kW of heat energy from one of those sources, and a corresponding release of various by-products into the environment (heat, CO2, etc.)
- That 1kW is then used to collect 3kW of energy from your garden.
- So to get 3kW of heat, you need 3kW of heat…
The question he then asks is, why not burn your own fossil fuels and cut out the middle man? And we had to admit that he has a point, but it was the anecdote we heard incidentally earlier that really made us listen.
An acquaintance of M. Bertrand had installed a geothermal system in a property with clay soil (like ours). In the beginning, all worked as advertised, but after a couple of years, the electricity bills began to mount, and the heating lost effectiveness. The gentleman in question was well equipped with the cash needed to solve the problem, so he had the garden re-excavated.
What he found was that the condensation caused by the captor coils in the ground had turned the surrounding clay to mud. When the mud dried, it caked hard, forming an effective shield between the moisture of the soil and the captors. The system was insulated against itself…
This could be taken as a cautionary tale about ensuring that there is enough sand placed about the coils at installation to avoid the problem, but having to factor precautions like that into a project take an expensive possibility and move it outside budget limitations.
“So what are you going to do now?” I hear you chorus.
I’ll tell you tomorrow.
22 November, 2004 — 15h29 (Paris) | energy
